ITP 150 Unit 4

What is conduction in energy?

Conduction of electricity is when electrons transfer between atoms in the conductor

Electron flow in conductors: why do metals conduct electricity well?

Metals are good conductors because they allow electric current to pass through them (electrons easily transfer) 

Unit of conductance, formula

Measured in siemens (G), formula: G = 1/R

How fast do electrons move in free space?

Electrons move at the speed of light (300,000,000 m/s)

How fast do electrons move in conductors?

50-60% of speed of light

AWG number increase vs. diameter change

As the AWG number increases, the diameter decreases 

Applications of AWG 10

dryers appliances, and air conditioning

Applications of AWG 12

appliances, laundry, and bathroom circuits

Applications of AWG 14

rental lighting and receptacle circuits

Stranded wire

flexible and easier to bend (more expensive) 

solid wire

more power (cheaper, and less flexible) 

Reasons for insulation

barrier against electric current entering body/objects, protective coating to resist chemical attack

examples of insulating materials

plastic, rubber, glass, cloth, wood

Conductor’s coding

AWG (diameter size), cable type and application (MTW: machine tool wire/appliances or THHN/THWN: thermoplastic high heat-resistant nylon for buildings), insulations maximum voltage rating

Factors affecting resistance

cross-sectional area (bigger area, lower resistance), Wire length (longer length, more resistance), Type of material *silver is the best, then copper, then aluminum), Temperature of material (higher temperature, higher resistance)

Voltage drop definition, allowable value

A loss in electrical pressure (voltage) usually in the form of heat to the environment caused by resistance of conductors or resistors, allowable value max of 3%

NEC, UL Special conductor pathways

NEC: National Electric Code for Electrical Systems in Construction 

UL: Underwriters Laboratories Inc. for electrical equipment like appliances and tools 

Conductor pathways: breadboards, printed circuit boards: mass production (chemical etching), and the automotive chassis ground

Resistor common wattage ratings

¼, ½, 1, 5, 10, 25 Watts

typical Ω values 

1Ω - 22 MΩ 

potentiometers and examples

Way to control the amount of power, manipulate electrical devices through sliding (dimmer switches and radio volume controls)

Common switch types

Roller switch, toggle switch

Ampacity

The current (in amperes) a switch can carry continuously under the conditions of use without exceeding its temperature rating

Toggle switches: functions

One path/one position, One path/two positions (two circuits), Simultaneously turning on each of the two circuits

Fuses: how do they protect?

Protect from a circuit overload, they will melt if there is too much current, and the fuse will break open and protect the rest of the circuit

Circuit breakers

Automatically operated electrical switches, will shut off if there is excess electrical current (overload)

Incandescent lamps

 least efficient, glass envelope with inert gas inside, tungsten filament and glass filament support, base with filament connections

Fluorescent lamps

mercury electrons bumped to higher energy levels and emit UV radiation, the radiation strikes a layer of phosphor coating releasing visible light (made of mercury, argon gas, phosphor coating, and a glass tube)

Neon light

The transformer outputs 10,000 V, and creates a current through neon gas to energize light, different glasses for different colors. (more efficient than fluorescent, fluorescent consumers up to 50% more energy than neon)

Light intensity: Lumens

the amount of light emitted by a standard candle falling on one square foot of a globe from one-foot radius

The standard unit for measuring conductor cross-sectional area

circular mils - one mil = 1/1000 inch

True or False: A 10 AWG conductor has a larger cross-sectional area than a 12 AWG  conductor.

True

True or False: A 22 AWG  conductor has more resistance per foot than # 6 conductor

True

A 20-amp lighting load is connected to a 120-volt AC source 300 feet away.  What is the voltage drop or loss caused by using a No. 12 aluminum wire?

38.4V

Formula for calculating CMA

CMA = (K)(I)(L)/(V.D)

Which of the following is an agency that tests safety features of home appliances and power hand tools?

UL

True or false: To control a lamp from two different locations, you would use  double-pole, double-throw switches

False

Which of the following materials is used in florescent lamps?

Mercury vapor, argon gas, phosphor coating

conductors are

pathways that allow electrons to flow through the electrical circuit

What do resistors do?

Restrict then current, drop the voltage

Power equation

P = E x I

Schematic Symbols: resistor

triangle line

Schematic Symbols: poteniometer

triangle line with extra arrow

Schematic Symbols: fuse

wave

Schematic Symbols: circuit breaker

hill over connected circuit